The present disclosure addresses methods and apparatus for distributed sensing of downhole properties; and more particularly relates to sensing of such downhole properties through use of magnetic sensors optically coupled to fiber optic cable.
Understanding the structure and properties of geological formations is important for a wide variety of functions in well and or reservoir management, monitoring and/or remediation. Measurements are commonly made in a borehole or formation (i.e., down hole measurements) are to provide data to aid in attaining this understanding, to identify the composition and distribution of material that surrounds the measurement device down hole. To obtain such measurements, magnetoelectric (ME) sensors may be used.
Among other applications, monitoring systems may use these measurements to monitor reservoirs while they are being flooded with water, steam or another substance to reduce the likelihood flood breakthroughs. While some ME sensors may not be sensitive enough for use in flood monitoring, ME sensors with increased sensitivity have recently become available. However, it may be difficult for systems at the surface to interface with multiple downhole ME sensors for effective high-sensitivity flood monitoring. Furthermore, some current methods for coupling to ME sensors may not permit permanent deployment of the ME sensors throughout the life cycle of the reservoir, thus necessitating stoppage of production during flood monitoring.